Docker: Difference between revisions

From Alpine Linux
(On a SBC board like a Raspberry Pi that lacks a battery to retain system time it's important for NTP to start and determine the current time before Docker starts. Otherwise a node in a swarm will reject CAs because they're from the future.)
 
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== Installation ==
== Installation ==


The Docker package is in the 'Community' repository. See [[Repositories]] how to add a repository.
The {{Pkg|docker}} package is in the ''community'' repository. See [[Repositories]] how to add a repository.


  apk add docker
  apk add docker


Connecting to the Docker daemon through its socket requires you to add yourself to the `docker` group.
Connecting to the Docker daemon through its socket requires you to add yourself to the <code>docker</code> group.


  addgroup username docker
  addgroup username docker


To start the Docker daemon at boot, see [[Alpine_Linux_Init_System]].
To start the Docker daemon at boot, see [[OpenRC]].


  rc-update add docker default
  rc-update add docker default
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=== Docker rootless ===
=== Docker rootless ===


Docker rootless allows unprivileged users to run the docker daemon and docker containers in user namespaces.
Docker rootless allows unprivileged users to run the docker daemon and docker containers in user namespaces. This is not the same as dockremap explained in the section below. With dockremap the daemon still runs as root.


This requires the <code>docker-rootless-extras</code> package and enabling the <code>cgroups</code> service:
This requires the {{Pkg|docker-rootless-extras}} package (available in ''community'') and enabling <code>cgroups v2</code>:
edit <code>/etc/rc.conf</code> and set <code>rc_cgroup_mode="unified"</code>. Then start the service on boot:


  rc-update add cgroups
  rc-update add cgroups
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=== Docker Compose ===
=== Docker Compose ===


'docker-compose' is in the 'Community' repository starting with Alpine Linux 3.10.
{{Pkg|docker-cli-compose}} is in the ''community'' repository starting with Alpine Linux 3.15.


  apk add docker-compose
  apk add docker-cli-compose


== Isolate containers with a user namespace ==
== Isolate containers with a user namespace ==
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</pre>
</pre>


add to '''/etc/docker/daemon.json'''
add to <code>/etc/docker/daemon.json</code>


<pre>
<pre>
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</pre>
</pre>


''You may also consider these options : '''
''You may also consider these options : ''
         "experimental": false,
         "experimental": false,
         "live-restore": true,
         "live-restore": true,
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         "no-new-privileges": false'''''
         "no-new-privileges": false'''''


You'll find all possible configurations here[https://docs.docker.com/engine/reference/commandline/dockerd/#daemon-configuration-file].
You'll find all possible configurations [https://docs.docker.com/engine/reference/commandline/dockerd/#daemon-configuration-file here].


== Example: How to install docker from Arch ==
== Example: How to install docker from Arch ==
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==== Alpine 3.8 ====
==== Alpine 3.8 ====
It may not have been the case before, but with Alpine 3.8, you must config cgroups properly
It may not have been the case before, but with Alpine 3.8, you must configure cgroups properly


'''''Warning''''': This seems ''not'' to work with Alpine 3.9 and Docker 18.06. Follow the instructions for grub or extlinux below instead.
{{Warning|This seems ''not'' to work with Alpine 3.9 and Docker 18.06. Follow the instructions for grub or extlinux below instead.}}


<pre>echo "cgroup /sys/fs/cgroup cgroup defaults 0 0" >> /etc/fstab</pre>
<pre>echo "cgroup /sys/fs/cgroup cgroup defaults 0 0" >> /etc/fstab</pre>
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== How to use docker ==
== How to use docker ==


The best documentation on using Docker and creating containers is at the [http://docs.docker.com/ official docker site]. Adding anything to it here would be redundant.
Check the [https://docs.docker.com/ official documentation] for details on general usage of docker, including creating and management of containers. Repeating these instructions here be redundant.


If you create an account at docker.com, you can browse through user images and learn from the syntax in contributed dockerfiles.
Public images can be browsed at the [https://hub.docker.com/ Docker Hub]. These should also serve as further reference on the Dockerfile format.


Official Docker image files are denoted on the website by a blue ribbon.
Official Docker image files are denoted on the website by a special badge.


== See also ==
== See also ==

Latest revision as of 07:53, 2 December 2023

Installation

The docker package is in the community repository. See Repositories how to add a repository. 

apk add docker

Connecting to the Docker daemon through its socket requires you to add yourself to the docker group. 

addgroup username docker

To start the Docker daemon at boot, see OpenRC. 

rc-update add docker default
service docker start

Docker rootless

Docker rootless allows unprivileged users to run the docker daemon and docker containers in user namespaces. This is not the same as dockremap explained in the section below. With dockremap the daemon still runs as root.

This requires the docker-rootless-extras package (available in community) and enabling cgroups v2: edit /etc/rc.conf and set rc_cgroup_mode="unified". Then start the service on boot: 

rc-update add cgroups

Additionally, the /etc/subuid and /etc/subgid files need to be set up as explained in the official documentation.

Docker Compose

docker-cli-compose is in the community repository starting with Alpine Linux 3.15. 

apk add docker-cli-compose

Isolate containers with a user namespace

adduser -SDHs /sbin/nologin dockremap
addgroup -S dockremap
echo dockremap:$(cat /etc/passwd|grep dockremap|cut -d: -f3):65536 >> /etc/subuid
echo dockremap:$(cat /etc/passwd|grep dockremap|cut -d: -f4):65536 >> /etc/subgid

add to /etc/docker/daemon.json 

{  
        "userns-remap": "dockremap"
}

You may also consider these options : 

       "experimental": false,
       "live-restore": true,
       "ipv6": false,
       "icc": false,
       "no-new-privileges": false

You'll find all possible configurations here.

Example: How to install docker from Arch

https://wiki.archlinux.org/index.php/Docker

"WARNING: No {swap,memory} limit support"

You might encounter this message when executing docker info. To correct this situation, we have to enable the cgroup_enable=memory swapaccount=1

Alpine 3.8

It may not have been the case before, but with Alpine 3.8, you must configure cgroups properly

Warning: This seems not to work with Alpine 3.9 and Docker 18.06. Follow the instructions for grub or extlinux below instead.


echo "cgroup /sys/fs/cgroup cgroup defaults 0 0" >> /etc/fstab
cat >> /etc/cgconfig.conf <<EOF
mount {
cpuacct = /cgroup/cpuacct;
memory = /cgroup/memory;
devices = /cgroup/devices;
freezer = /cgroup/freezer;
net_cls = /cgroup/net_cls;
blkio = /cgroup/blkio;
cpuset = /cgroup/cpuset;
cpu = /cgroup/cpu;
}
EOF

Grub

If you use Grub, add the cgroup condition into /etc/default/grub, then upgrade your grub 

GRUB_CMDLINE_LINUX_DEFAULT="... cgroup_enable=memory swapaccount=1"

Extlinux

With Extlinux, you add the cgroup condition, but inside of /etc/update-extlinux.conf 

default_kernel_opts="... cgroup_enable=memory swapaccount=1"

then update the config and reboot

update-extlinux

How to use docker

Check the official documentation for details on general usage of docker, including creating and management of containers. Repeating these instructions here be redundant.

Public images can be browsed at the Docker Hub. These should also serve as further reference on the Dockerfile format.

Official Docker image files are denoted on the website by a special badge.

See also

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